Enabling data URI image uploads

[andrewhayward]

Not sure where's best to include tests for this.

[brianloveswords]

I think this line might be a little too clever, it's hard to tell at a glance what's going on. Should probably break it into steps.

Alternatively, you can probably use url.parse:

const scheme = urlUtil.parse('' + url).scheme
if (scheme === 'data:')
  return createFromData(url, callback);

[brianloveswords]

As for tests, I'd create a new test file for image-helper stuff.